1. Field of the Invention
The present invention relates to a photographic film cassette and a camera for use therewith. More particularly, the present invention relates to an improvement of a photographic film cassette in which a leader of a photographic film can be advanced to the outside of a cassette shell when a spool is rotated in an unwinding direction, and a camera suitable for use with the novel cassette.
2. Description of the Related Art
A known photographic film cassette includes a photographic film positioned so that a leader does not protrude from the cassette shell prior to loading the cassette in a camera. Such a cassette is easily loaded into a camera. A simple photographic film-transporting mechanism of the camera is typically used with this type of cassette, and includes a construction which rotates a spool to unwind a photographic film strip (hereinafter called as film), thereby causing the leader to move through a passageway for the photographic film and exit from the cassette, as suggested in U.S. Pat. Nos. 4,834,306 and 4,832,275.
To advance the leader outward by rotating the spool, the cassette requires a structure for transmitting rotation of the spool to a roll of the photographic film. It is known to provide the inside of the cassette shell with arcuate ridges to be in contact with the roll so as to prevent the roll from loosening and thus transmit rotation of the speed to the film. The photographic film presses itself against the arcuate ridges, due to its tendency to recover a straight form. To cause the leader to exit through a passage mouth of the cassette shell, it is known to utilize a separator claw arranged inside the cassette shell so as to abut upon the leader. During rotation of the roll, the leader abuts upon the separator claw, which separates the leader from the roll so as to direct the leader toward the passage mouth, until the leader exits from the cassette to be received by the camera.
To prevent ambient light from entering the cassette shell, light-trapping ribbons having pile threads are conventionally attached to the inside of the passageway. It is also disclosed in Japanese Patent Laid-open Publication No. 3-37645 (corresponding to U.S. patent application Ser. No. 07/870,212 and EP 0 406 815 A2) that a moveable cover member may be positioned over the passage mouth so as to prevent light from entering the cassette shell. The cover member is released from a locking mechanism and opened by a camera, when the camera is loaded with the cassette, e.g. in response to closing a door of a cassette receiving chamber. When the cover member is open, the advancing mechanism incorporated in the camera rotates the spool in the unwinding direction so as to advance the leader out of the cassette. The cover member is closed when the photographic film is wound back into the cassette shell after the exposure of the photographic film is completed. The closed cover member is then locked, e.g. in response to opening of the chamber door. The closed cover member serves to protect the exposed photographic film inside from being subjected to ambient light inadvertently.
There is, however, a problem in the above cassettes in that the emulsion surface of the photographic film is sometimes scratched or damaged. In particular, during transportation of the photographic film for advancement or rewinding, the photographic film comes in direct sliding contact with relevant portions of the plastic cassette shell, such as the separator claw and edges of the passage mouth. Although the light-trapping ribbon can come into contact with the photographic film without damaging it, the photographic film may become damaged due to frictional contact with the separator claw and/or the wall inside the passageway. Also, in such a case, dust is created from both the emulsion surface and the back surface of the photographic film, and the dust may adhere on the image frames on the photographic film. This can hinder the development process.